Ultrasound Physics & Doppler Principles Flashcards

Which artifact can cause a vessel to appear to contain echoes when it is truly anechoic, due to sound energy arriving from outside the main beam?

Answer: Side lobe artifact

Side lobe artifacts arise from off-axis energy that returns echoes misregistered as if from the main beam, creating false internal echoes in vessels.

The time-gain compensation (TGC) control on an ultrasound system is designed to compensate for:

Answer: Depth-dependent attenuation of the ultrasound beam

TGC amplifies deeper returning echoes more than superficial ones to correct for signal loss due to attenuation with depth.

A mirror-image Doppler artifact most commonly occurs:

Answer: Below a strong specular reflector such as the pleura or diaphragm

Strong specular reflectors like the diaphragm or pleura create a mirror-image of Doppler signals on the opposite side of the reflector.

What is the primary advantage of power Doppler (color power angiography) over conventional color flow Doppler?

Answer: It is more sensitive to slow flow and small vessels

Power Doppler encodes the amplitude (power) of the Doppler signal rather than frequency shift, making it more sensitive to slow flow in small vessels.

Which statement about lateral resolution in ultrasound imaging is correct?

Answer: Lateral resolution is best at the focal zone where the beam is narrowest

Lateral resolution is determined by beam width and is optimal at the focal zone where the beam is most narrowly focused.

In the context of vascular ultrasound, 'end-diastolic velocity' (EDV) is measured at which point on the spectral waveform?

Answer: The lowest point of the waveform immediately before the next systolic upstroke

EDV is the velocity at end-diastole, recorded at the lowest point of the waveform just before the next systolic peak rises.

When performing a Doppler examination, reducing the sample volume size will:

Answer: Isolate flow from a smaller region, reducing spectral broadening

A smaller sample volume samples fewer laminar layers, reducing the range of detected velocities and narrowing the spectral envelope.